The effects of eating versus fasting(before doing exercise) on gene expression in adipose (fat) tissue in response to exercise are different. Gene expression in the adipose tissue differed significantly in both cases. The expression of two genes, PDK4 and HSL, increases when we fast and exercise in empty stomach and decreases when they eat before exercising. The rise in PDK4 likely indicates that stored fat is used to fuel metabolism during exercise instead of carbohydrates from the recent meal. HSL typically increases when adipose tissue uses stored energy to support increased activity, such as during exercise.
Adipose tissue often faces competing challenges. After eating, adipose tissue "is busy responding to the meal and a bout of exercise at this time will not stimulate the same [beneficial] changes in adipose tissue. This means that exercise in a fasted state might provoke more favourable changes in adipose tissue, and this could be beneficial for health in the long term.
It is a matter of choice depending on how your body stimulates to it.
However, taking the right nutrients after you exercise is just as important as what you eat before.
The most important thing is to understand how the right foods can help you after exercise, it's important to understand how your body is affected by physical activity.
On a long bike ride, I even eat while I'm exercising, but I notice I get a better quality of fuel when I start burning fat, as detailed by @Crypto-wisdom.